Diagram to show sequence of events leading to clumping of red blood cells in a rhesus positive (Rh+) fetus in a rhesus negative (Rh-) mother during second preganancy.
A,B    First preganancy
A    Fetal red blood cells pass into mother's blood stream by damage to the palcenta
B    Anti-Rh+ antibodies appear in mother's blood
C,D    Second pregnancy
C    Anti-Rh+ antibodies pass from mother's blood stream to fetal blood stream
D    Reaction of Rh+ antigen on fetal red blood cells and Rh+ antibody causes clumping of fetal red blood cells
E    Fetal red blood cell with Rh+ antigen
F    Rh+ antibody
1    Placenta
1a    Mother's blood stream
1b    Fetal blood stream
2    Umbilical cord
3    Fetus